Method of waterproofing sheathing for electrical conductors and the product thereof



April 21, 1931.

.J. KENNEDY 1,801,813 METHOD OF WATE ING SHEATHING FOR ELECTRICAL CONDUCT AND THE PRODUCT THEREOF Filed Oct. 4, 1928 Patented Apr. 21, 1931 UNITED STATES PATENT OFFICE JOSEPH A. KENNEDY, OF PAWTUCKET, RHODE ISLAND, ASSIGNOR, BY MESNE ASSIGN- MENTS, TO ANACON'DA WIRE AN D CABLE COMPANY, A CORPORATION OF DELAWARE METHOD WATERPROOFING SHEATHING FOB, ELECTRICAL CONDUCTOBS AND THE PRODUCT THEREOF Application filed. October 4, 1928. Serial No. 310,269.

The present invention relates to flexible woven or braided sheathing for electrical conductors, and particularly to a method of water-proofing t e same by which the sepa- 8 rate strands of such sheathing are independently impregnated with the waterproofing substance or compound prior to being interwoven or otherwise interlocked with one another. The term sheathing 10 as used in the title and specification of this patent is a comprehensive term; and includes not onl the casing or jacket which is commonl raided or woven outside of the insulation of sin 1e wires and around a collection of wires orming a cable (when such conductors are made fire-proof and waterproof conformably to the rules of the Fire Underwriters), but also electrical conduit which is constructed as open tubing adapted to receive wires after completion thereof.

The object of the invention is to effect a more thorough impregnation of the strands or components of the sheathing than can be done b simply dipping or immersing the complete sheathing 1n the water-proofing compound, and to make the completed sheathing better receptive of subsequently applied compounds for waterproofing and fire-proofing than are those made of 'untreated strands. The treatment according to this invention is applicable to the component elements of any such sheathing made of fibrous strands, whatever the specific nature of the strands may be. That is, conduit of the nature herein referred to is frequently woven with cotton yarns as the warp strands, and twisted paper strands for the weft or filling, and the treatment applies to both of these types of strand. -A

subordinate feature of theinvention involves a s ecial mode of treating the strips out of which such paper strands are made in the course of their conversion from fiat strips to twisted strands or yarns.

I have illustrated in the drawings my new step of impregnating paper strands above referred to, but have not illustrated that of impre natin strands already spun or twiste as t e latter involves only dipping a spool or bobbin of the yarn in the impregnating substance, or drawing the yarn through a bath of the substance before winding, procedures which are individually old in themselves and so well understood as to require no illustration.

In the drawing, Fig. 1 is a diagrammatic view showing the principles of means for transforming a flat strip of paper into a strand suitable for weaving, together with operative means for applying the fire-proofing substance to the strip in the course of its transformation to the twisted state.

Fig. 2 is a view, partl in section and partly in elevation, of a f i'agment of completed electrical conduit made of strands treated according to this invention.

I will first describe the particular method of impre nating the paper cord with the compoun referring to the above described drawing. a represents a roll of paper suitably strong, tough and flexible to be twisted into a strand suitable for Weaving, and out to the form of a strip or ribbon b having the right width. The strip passes to a die 0 by which it is crumpled together, and thence to a spinning or twisting machine, such as the well-known Brownell twister by which it is given the required twist, finally bein wound up on a spool, bobbin or tube e. E false twist device is shown at d, simply as an illustration of means cooperative to the result of converting a fiat strip into a strand of circular cross-section. Twisting machines have long been known and used, wherefore I have not intended to show any such machine in detail here, but onl to indicate diagrammatically such a trans ormation of a strip, my main purpose here being to show the provisions which I have made for impregnating the paper strand. Such means comprises a-tank f containing the water-proofing substance from which a leader 9 passes into light contact with a vertical stretch b of the strip in advance of the die. The leader may be a flat strip of metal on which the water-proofing substance drips from a hole in the bottom of the tank, or it may be a tube passing from thetank and having communication with its interior, or may be of other construction. An important fact is that it conveys the water-proofing substance to the paper while the latter is in an outspread open condition and thus best adapted to receive and absorb the compound. This substance soaks into the paper and spreads through the fibers thereof, the spreading effect being assisted by the gathering 1n and crumpling of the paper by means of the die, which occurs immediately after the compound has been brought to the paper and before it has had time to dry.

The compound or substance used for this purpose may be any of the compounds suitable for waterproofing structures of the character described. I prefer to use a solution of asphaltum in light hydrocarbon oil, such as kerosene, gasolene, benzine, etc., or other solvent; the solution being of such fluidity that it will flow freely and instantly soak into the paper and spread among the fibers thereof when at the ordinary room temperatures. That is, the compound requires no application of artificial heat to make it fluid.

Cotton yarns or strands are most easily impregnated by being dipped into a tank of the water-proofing solution after being wound on a spool, bobbin, tube, or the like. Such a wound accumulation of yarn may be dipped by hand or mechanically. So also may a similar wound accumulation of the paper cord be dipped; although the treatment of paper in this manner is less effective thanin the mode first described, as the twisted strand does not soak up the compound so readily and rapidly as the untwisted open strip. Cotton yarn, however, even when wound on a spool, takes up the compound readily and is thoroughly soaked or becomes thoroughly impregnated from a single brief dip. The dipping solution is preferably of the same fluidity as that used for impregnating the paper in the first described method. A wide latitude in the degree of fluidity is possible, however.

Either the cotton yarn before being wound up, or the paper strip before being twisted, may be impregnated by passing through a. tank or bath of the compound if desired.

Upon evaporation of the solvent in the solution of impregnating compound, the strands of either character (that is, cotton yarns or twisted paper cords) are left inga dry condition containing the water-proofing substance thoroughly distributed among their-fibers. But owing to the thinness (fluidity) of the solution, the dry residue adheres to the fibers rather than to the out side of the strand and does not fill the interspaces among the fibers. Thus the flexibility of the strands is not sensibly diminished; and although the compound may not wholly exclude moisture from between the fibers, it does substantially exclude water from direct contact with them and so protects them from the rotting effect consequent upon wetting.

As previously stated, the yarns or strands so treated, either the cotton strands alone or the paper strands alone, may be braided or woven into a sheathing, as both warp and weft in a woven structure, or the cotton and paper yarns may be combined together in a woven structure, those of one class servin as warp and the other as filling. Tubes an jackets so made are particularly receptive to subsequently applied compounds for either water-proofing or fire-proofing when passed through a mass of such compounds, provided the compounds then used are of a re lated nature; that is, for example, if the inipregnating and subsequent water-proofing or fire-proofing substances are both hydrocarbons. In such cases the after applied compound forms a homogeneous union with the impregnating substance, making the finished article highly resistant to penetration of water, either through the meshes of the weave, or between the fibers of the strands, or into direct contact with the fibers. This after applied compound is prevented, by the closeness of the weave, its own viscosity, and the method of applying it commonly practiced in this art, from passing through the wall of the sheath and either obstructing its bore, in the case of an open conduit, or reaching the interior conductors, in the case of a cable or wire about which the sheath has been constructed, as in the case of sheathed conductors and electrical cable.

A very important attribute of the sheathing made according to this invention is that, although the individual strands are thoroughly waterproof, yet they are dry and non-tacky when woven into a sheath. Hence the waterproofing compound does not coat or soil the conductors of the enclosed cable and does not obliterate the polarity marks of the wires nor saturate the filler strands or cords which are commonly laid with the wires of an electrical cable to fill the grooves between them and give roundness to the sheathing when braided in place upon them. The polarity marks above referred to consist usually of different colors or colored strands in the woven coverings of different wires composing an electrical cable, to distinguish the wires of different polarity or those designed to be connected in difierent circuits. When the outer sheathings of such cables are saturated in the way usually practised heretofore, the compound is liable to soak through the sheathing and discolor the wires, obscuring or obliterating such polarity marks. This invention avoids liability of such discoloration.

What I claim and desire to secure by Letters Patent is:

1. The method of making a water-proof sheathing of the character set forth, which consists in impregnating the component strands of such sheathing in a solution of water-proofing material prior to combining them into a sheathing, dryin the strands to render them non-sticky, then interconnecting such strands as a sheathing, and then applying to the sheathing a waterproofing compound having affinity for that previously applied to the separate strands.

2. The method of making a waterproof sheathing of the character set forth which consists in first impregnating such strands with a highly fluid solution of a water-repellent substance in a volatile solvent, drying the strands so impre ated to render them non-sticky, and su sequently interconnecting such dried strands into a sheath of the desired construction.

3. The method of making a sheath of the character described containing paper strands which consists in first impregnating the paper strips of which the strands are formed with a thin solution of water-proofing compound in a volatile solvent and twisting such strips, drying the strands so formed, and interweaving all the component strands of the fabric, including those so treated, into a sheathing.

4. The method ofproducing a water-proof sheathing of interwoven cotton and paper strands which consists in separately impregnating the cotton strands and the paper strips from which the paper strands are made with a thin solution of a water-resistant substance in a volatile solvent, twisting the paper strips into cords, drying all the strands, and interweavin the cotton and paper strands together while in the dry state to form a sheath.

5. The method of producing a water-proof sheath which consists in impregnating cotton strands with a thin solution of asphaltum in a volatile solvent, drying such strands, impregnating paper strips with a solution of the same character and twisting such strips into strands, drying all of the strands so impregnated, and interweaving the paper strands with the cotton strands into a tubular sheath.

6. The method of preparin strand as a component of a s eath for electrical conductors, which consists in roviding a strip or ribbon of tolligh, flexible and porous paper, pro essive im re natin such strip with a thir i soluti n of iisl halturi in a volatile solvent and subsequentl progressively twisting the so impregnate strip into a strand or cord, and drying such cord prior to interweaving it with other strands.

7. A sheathing as and for the purposes a water-proof set forth comprising interconnected strands,

each of which have been impregnated prior to weaving with a thin solution of asphaltum signature.

JOSEPH A. KENNEDY. 

